I would agree with you here because you make sense. However, this has never been my experience while testing any intakes on any of my cars on the dyno. I have always gained power with two exceptions. And that was on a old crown victoria. After the dyno operator added fuel, the gains could be seen then. And also on an old Subaru RX turbo (Just sticking an air filter on this one made no change).

 

That is correct but what I meant by it is no matter how much air the motor ingests from the intake it will always be limited to the heads internals.

Its like walking into a cave with a group of friends and all fitting but to continue through the cavern you must all walk one after another because of space constraints.

I mentioned AFR because no matter how much air that's introduced the TB will be the first limiting factor and the ecu will add as much fuel needed to achieve the factory tunes requirements.

Most cars do run rich to be safe and account for user error ie adding bolt ons with no tune lol

 

yes, our throttlebody is suffocating! But so is our intake manifold design.


If someone could replecate the K series style and offer it for sale, I think lots of power would be opened up at sacrifice of lowend torque

 

I've had the HPS Intake for a couple months now and I'm still happy with it. The best mileage I had out of my Fit in the previous 3 months of ownership was 37mpg of all highway driving, just me in the car, and no A/C. Since then I have had 3 different tanks of just over 40mpg, all highway (calculating mileage, not using the car's numbers). The last tank was with 3 adults in the car and the A/C running full blast the whole time. I know there are a ton of things that go into mileage a car gets so who knows if the increase is due to the intake, but I'm a believer.
The sound is nice and is not noticeable at all until you are pushing the car. I have not noticed any decrease in power at any rpm. Hard to say if there is an increase, but maybe a little bit in low rpm.

 

I have my KNN drop in for sale if anyone is interested. I used it for less than 800 miles. Still in the box. $25 shipped. Still perfectly clean and oiled.

 

Hope you enjoy the sound. I like OEM and for autocrossing my money is better spent on tires and suspension.

The reason why the engine feels like its starved for air at high rpms is because our cars don't have vtec if you look at the dyno charts torque drops off above 6000rpms. Which gives you the feeling its starved for air. I-vtec kicks in between 2-3k, and makes the motor go from 12V to 16V. It gives the motor better low end torque and fuel economy.
The last gen civic si had both systems which has made it a bit confusing, even I was confused lol.

As far as power, there is a forum post someone did do a dyno just after installing an intake and exhaust and gained 15whp over stock which would be noticeable. The problem is the ECU is designed to tune for fuel economy and not power. He redid the dyno 2 weeks later and the car was back to stock power. Although you do get better fuel economy as you noticed less resistance means better efficiency which means less fuel consumption.

To see 15whp you are gonna have to spend an additional couple hundred bucks for a piggyback ECU to make it use that extra efficiency for power. So you are spending ~$100/hp which is really expensive. And you have to do both if anything the exhaust may be more limiting usually.

I personally don't like K&Ns or other oiled filters because there is risk it can plug your MAF sensor with oil which will cause your engine to act weird. Not worth voiding engine warranty over a bit more money for a dry filter.

When I autocross my fit and I usually leave the hood open between runs to vent heat. That alone probably gives you back a few hp because the heat would otherwise be radiating into the engine bay and between the grid and start you don't have enough speed to produce flow of cool air into the engine bay and is probably all the charts from K&N, AEM, etc show.

 

This is only true for the GD's L15A1.

GE's L15A7 has standard iVTEC that engages at 5500 RPM. It runs 16 valve all the time.

AFAIK reliable sources on here said the throttlebody is in no way the limiting factor to power (to the point most people here take the motor to), but more so the intake manifold. They did maths to prove it.

There are larger TB available for L15 in asia that are bolt on, Spoon make the venturi TB and M&M Honda has larger TBs, but I don't think they're needed unless you do some serious motor work. You can get them through Nengun or another importer i'm sure.

http://www.mandm-honda.com/gd_intake.html

 

Something doesn't add up. I'm new here so my apologies ahead of time. The dyno charts posted in this thread are not showing a power surge where iVTEC engages at 5500rpm. Why is that?

Either the dyno charts are not representative of GE, the GE doesn't engage at 5500rpm or iVTEC doesn't give a boost of power.

Can anyone please explain this? I'm a Subaru guy so not used to this but you can understand my thinking on this I hope.

 

A PROPERLY setup VTEC system does not show a big surge of power. Just as the low cam profile is starting to lose its peak power, the high cam profile kicks in. Honda did traditional VTEC on the L15A7 to increase motor efficiency. The GD gets better mileage due to being lighter weight and being able to stay in 8 valve mode if you keep the rpms lower then 2500-2700

 

So based on what you are saying (Maybe me saying 'boost of power' is throwing things off base), when the low cam profile is starting to lose it's peak power, the high cam profile kicks in. Would you agree that in both dyno's you see, the torque starts to drop between 3500rpm and 4000rpm before rising again?

Also, both dyno's look like torque starts to finally fall off a 2nd time around 4800rpm or so. It doesn't seem like a high cam profile is kicking in at 5500rpm. Hence my original question.

Thanks for the explanation.

 

On the L15A7, Honda developed a special chamber in the manifold (under the "honda" text) that created a torque peak around 3500rpms. This was to assist the low cam profile, and as power slightly dips towards 4200-4600rpms or so, the high cam profile kicks in past 5k rpm to remind you that this tiny 1.5L still has some balls left

lol

 

Yes, designed with linear power delivery. There may be a few small dips here and there but nothing crazy like the old VTEC dyno charts.

There's no VTEC KICKED IN YO feeling, though you can hear the induction noise change when the high cam kicks in around 5500... well at least I can.

 

Thanks! I know next to nothing about Hondas. I'm still back in the early 'VTEC Kicked In Yo' years. Technology has allowed the two cams to work seamlessly to make a smooth powerband now. Amazing! Thanks!

 

No problem, that's part of what put the "i" in i-VTEC. More intelligent than it used to be, the PCM now uses throttle position, engine load, etc, etc, to activate VTEC. The system is just generally smoother than it used to be through engine design.

Go look at K series i-VTEC dynos and you will see similar, slight dip before engagement but smooth in general. AFAIK the actual mechanical engagement is still oil pressure controlled, but the PCM takes more perimeters into consideration.

 

If you wanna compare I-VTEC dyno to 1st gen VTEC the engine that yielded the most drastic change at VTEC x-over, look at a B16A power curve. When VTEC came in at 6000 rpm there was a huge jump in torque. Anywhere from 15 to 20 ft/lbs. Original VTEC had the best surge. Almost like a 2nd stage turbo (especially the H22A in the Prelude) feeling. This was duh to the fact that the low cam was loosing steam 500 rpm before VTEC came in. To fix this, we'd install VTEC controllers to lower the the VTEC x-over point to just b4 the rpm when the low cam started to loose power. This would make the power more linear just like what i-VTEC current does. This is why you dont see many (if any) people adding the Apex-i VTEC controllers on cars with I-VTEC. The L15A7 to me feels/sounds like a baby brother to the B16A from the best most raw Civic SI. The '99-'00 Model. Anyone else care to opine on this? Id love to read what other loyal honda/acura (I'm on car 13 since '98).

I wanna also comment on power mods. I think after owning this car for 2mo the best mod was switching from 87 octane to 93. The reason being that this engine was made run on low octane by Japanese standard which is 94-95 octane. The low octane here in the states tends to make the L15A7 knock a little. I noticed (or my butt did) a decent power gain (5hp/3tq) in mid range to top. It doesn't feel like the engine is "choking" from 6500 to 7000. All im saying is try it out for yourselves and see.

 

I purchased an HPS intake. The inside of the tubing threw me off a bit. The HPS tubing diameter is the same as the stock throttle body. However, the inside diameter is a little smaller. It appears there is another pipe inside the HPS piping and they welded it to the outside pipe that you actually see.

So the difference in diameter between that outside piping and inside piping looks to be smaller overall than that of the stock maf sensor housing diameter.

 

Because the stock piping size Honda gave the Fit is already plenty big enough.

That's why you won't see noticeable power gains. Shortening the intake with the cone filter just changes the harmonics and bumps top end. Power is not free unless there are restrictions, and on this motor the intake is not one of them.

If anything HPS made the interior piping smaller to increase velocity and somewhat make up for the loss of low end torque due to the shorter length. You may gain some power up top but not because the piping was a restriction.

At the end of the day I don't think you need to be too sad, the HPS piping couples to the MAF cutout and then to the TB right? Smaller to bigger is ok in this case I think at least that's what I see in my mind, someone correct me if that's backwards.

 

its not about what is the biggest size, that is not always what's appropriate. It needs to complement the other components. The difference beween your DIY, low-budget offerings, and respected big-firm offerings is: the amount of R&D that is done, access to fractional differences in piping diameter sizing, and testing that it plays well with MAF calibration.... and carb certification. I you're budget or low volume, you might be limited to pipe offerings of 2 and 2.5" diameter, maybe 2.25 is the ideal solution but is hard to source a supplier. If you are big enough of an operation, you can probably source 2.38" if that is the sweet spot. And don't think a company going through carb certification doesn't impact cost. You pay to play, and yes, there are no guarantees of additional gains, but it should help confidence levels.

I like short rams. I like removing those 9-10 90 degree bends and additional baffolding. It makes the engine a bit more twitchy if nothing else. I'll definitely say there was a power bump but also the ECU adapted very quickly and I think most of those gains were moot. I could certainly pull the negative terminal every day and reset things if I was so inclined but alternatively, it was a small bump in mpg, It is a welcome improvement regardless of where it was ultimately realized.

 

factory MAF tube gets smaller at sensor. if HPS changed the diameter, there would be a shitty fuel trim and car would lose power

 

I notice this 'barely' after rubbing my hands inside the stock maf sensor housing over and over again. It tapers in so gradually, it's very hard to tell that its getting smaller. You are correct though in that HPS had to do this so that the maf sensor could calculate the air correctly. I actually feel better now that the piping inside the HPS intake stays small only long enough for the air to be measured by the maf sensor, then it immediately opens back up to the outer diameter piping size.

Looking forward to utilizing this piece of intake.